Undular bores, or dispersive shock waves, are non-stationary waves propagating as oscillatory transitions between two basic states, in which the oscillatory structure gradually expands and grows in amplitude with distance travelled. The generation of undular bores in polymethylmethacrylate (PMMA) bars following tensile fracture is observed using high-speed pointwise photoelasticity. We show that a viscoelastic extended Korteweg - de Vries (veKdV) equation provides good agreement with the key observed experimental features of the generated bores for a suitable choice of material parameters. Linearisation of the veKdV equation near the pre-strain level prior to fracture captures some features at the front of the bore. We analyse the behaviour of the bores following both natural and induced tensile fracture. We also vary the cross section of the waveguide and conditions at fracture. Such waves could be present in the signals generated by fracking, earthquakes and other events involving transverse fracture of an appropriately pre-strained waveguide. Joint work with Curtis Hooper, Pablo Ruiz and Jonathan Huntley.

References :
[1] C.G. Hooper, P.D. Ruiz, J.M. Huntley, K.R. Khusnutdinova, Undular bores generated by fracture, Phys. Rev. E 104, 044207 (2021).
[2] C.G. Hooper, K.R. Khusnutdinova, J.M. Huntley, P.D. Ruiz, Theoretical estimates of the parameters of longitudinal undular bores in PMMA bars based on their measured initial speeds, arXiv:2110.11843v1 [physics.class-ph] (2021).